The muscle Z band: lessons in stress management.

Two of the most characteristic features of striated muscle are (i) its ability to contract and generate tension when activated and (ii) its ability to return to its original length and form after contraction or stretching ceases. These two properties are to a large extent the primary manifestations of separate sets of filament systems: contractile actin and myosin filaments and viscoelastic titin and intermediate filaments. Z bands function as a common link that mechanically integrates contractile and elastic elements and as such they play a fundamental role in transmission of active and passive forces. Differences in Z band structure have been described for distinct classes of muscle and fibre types. The diversity in Z band architecture has been built around its phylogenetically conserved role as an actin-anchoring structure. Novel proteins are likely to account for structural and functional differences seen across the phyla.